Very disappointed to find that Disk Director 12.5 still does not support EXT4 partitions despite this being offered by nearly all competitive disk management products, especially given that DD 12.5 suggests that such EXT4 partitions are not formatted!

if I change a partition on a usb stick or an external disk, DD 12.1 / 2 wants to reboot.

Why is there necessary or what should that be?

Acronis Disk Director might require you to reboot your computer if the partition involved in the operation cannot be locked (for instance, contains open files). In this case, Acronis Disk Director prompts you to reboot the computer after you commit the operation. Please note that the system partition (the partition the operating system files are stored on) always contains open files.

If the target disk has/had a previous install of another operating system then this may cause the clone to ask for a reboot.